- ID:
- ivo://CDS.VizieR/J/PASJ/60/739
- Title:
- Emission-line stars in the W5E HII region
- Short Name:
- J/PASJ/60/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made a new survey of emission-line stars in the W5 E HII region to investigate the population of PMS stars near the OB stars by using the Wide Field Grism Spectrograph 2 (WFGS2). A total of 139 Halpha emission stars were detected and their g'i'-photometry was performed. Their spatial distribution shows three aggregates, i.e., two aggregates near the bright-rimmed clouds at the edge of the W5 E HII region (BRC 13 and BRC 14) and one near the exciting O7V star. The age and mass of each Halpha star were estimated from an extinction-corrected color-magnitude diagram and theoretical evolutionary tracks. We found, for the first time in this region, that the young stars near the exciting star are systematically older (4Myr) than those near the edge of the HII region (1Myr). This result supports that the formation of stars proceeds sequentially from the center of HII region to the eastern bright rim. We further suggest a possibility that the birth of low-mass stars near the exciting star of the HII region precedes the production of massive OB stars in the pre-existing molecular cloud.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/430/911
- Title:
- Expansive components in HII regions
- Short Name:
- J/A+A/430/911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the presence of low intensity high velocity components, which we have termed wing features in the integrated Halpha emission line profiles of the HII region populations of the spiral barred galaxies NGC 1530, NGC 3359 and NGC 6951. We find that more than a third of the HII region line profiles in each galaxy show these components.
- ID:
- ivo://CDS.VizieR/J/MNRAS/490/5063
- Title:
- Extended sources in SCORPIO at 2.1GHz
- Short Name:
- J/MNRAS/490/5063
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of a large sample of extended radio sources in the Stellar Continuum Originating from Radio Physics In Ourgalaxy (SCORPIO) field, observed and resolved by the Australia Telescope Compact Array. SCORPIO, a pathfinder project for addressing the early operations of the Australia SKA Pathfinder, is a survey of ~5 square degrees between 1.4 and 3.1GHz, centred at l=343.5{deg}, b=0.75{deg}, and with an angular resolution of about 10 arcsec. It is aimed at understanding the scientific and technical challenges to be faced by future Galactic surveys. With a mean sensitivity around 100uJy/beam and the possibility to recover angular scales at least up to 4 arcmin, we extracted 99 extended sources, 35 of them detected for the first time. Among the 64 known sources 55 had at least a tentative classification in literature. Studying the radio morphology and comparing the radio emission with infrared we propose as candidates six new HII regions, two new planetary nebulae, two new luminous blue variable or Wolf-Rayet stars, and three new supernova remnants. This study provides an overview of the potentiality of future radio surveys in terms of Galactic source extraction and characterization and a discussion on the difficulty to reduce and analyse interferometric data on the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A38
- Title:
- Extinction map of OMC-1
- Short Name:
- J/A+A/533/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Orion Nebula and its associated young stellar cluster are located at the front-side of the optically thick OMC-1 molecular cloud. In order to disentangle the cluster members from background contamination, it is important to know the extinction provided by the OMC-1, which is poorly known, the available measurements yielding contradictory results. Our main goal is to derive a new extinction map of the OMC-1, obtaining information about the structure of the OMC-1 and the Orion Nebula Cluster. The most recent near-infrared catalog of stars is used to study the distribution of reddening across a 0.3deg^2^ area covering the Orion Nebula Cluster. On the basis of the observed (H,H-Ks) diagram, we establish a criterion for disentangling contaminants from bona-fide cluster members. For contaminant stars, interstellar reddenings are estimated by comparison with a synthetic galactic model. A statistical analysis is then performed to consistently account for local extinction, reddening and star-counts analysis. We derive the extinction map of the OMC-1 with angular resolution <5'. We also assemble a sample of candidate cluster members, for which we measure the extinction provided by the nebular environment. These extinction measurements are analyzed similarly to the contaminant sample, and an extinction map of the Orion Nebula is derived. The extinction provided by the OMC-1 is variable on spatial scales of a few arcminutes, while showing a general increase from the outskirts (A_V_~6) to the direction of the Trapezium asterism (A_V_>30). The Orion Nebula extinction map is more irregular and optically thinner, with Av of the order of a few magnitudes. Both maps are consistent with the optical morphology, in particular the Dark Bay to the north-east of the Trapezium. Both maps also show the presence of a north-south high-density ridge, which confirms the filamentary structure of the Orion molecular complex inside which star formation is still taking place.
- ID:
- ivo://CDS.VizieR/J/ApJ/559/864
- Title:
- Extragalactic ultracompact H II regions
- Short Name:
- J/ApJ/559/864
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the detection of optically thick free-free radio sources in the galaxies M33, NGC 253, and NGC 6946 using data in the literature. We interpret these sources as being young embedded star birth regions that are likely to be clusters of ultracompact H II regions. All 35 of the sources presented in this article have positive radio spectral indices ({alpha}>0 for S_{nu}_){prop.to}{nu}^{alpha}^), suggesting an optically thick thermal bremsstrahlung origin from the H II region surrounding the hot stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/120/113
- Title:
- Faint Emission Lines and Temperature
- Short Name:
- J/ApJS/120/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present echelle spectroscopy in the 3500-10300{AA} range of the Hourglass Nebula, which is embedded in the Galactic H II region M8. The data were obtained using the 2.1m telescope at Observatorio Astronomico Nacional in San Pedro Mqrtir, Baja California. We have measured the intensities of 274 emission lines, in particular 88 permitted lines of C^+^, N^0^, N^+^, O^0^, O^+^, Ne^0^, S^0^, S^+^, Si^0^, Si^+^, and Si^++^, some of them produced by recombination only and others mainly by fluorescence. We have determined electron temperatures and densities using different line intensity ratios. We derive the He^+^, C^++^, O^+^, and O^++^ ionic abundances as well as - for the first time in a nebular object - the total O abundance from recombination lines; these nebular values are independent of the temperature structure of the nebula. We have also derived abundances from collisionally excited lines for a large number of ions and elements; these abundances do depend on the temperature structure. Accurate t^2^ values have been derived by comparing the C^++^, O^+^, and O^++^ ionic abundances obtained making use of both collisionally excited lines and recombination lines. A comparison of the solar, Orion Nebula, and M8 chemical abundances is made.
- ID:
- ivo://CDS.VizieR/J/MNRAS/368/253
- Title:
- Faint emission lines in M16, M20, NGC 3603
- Short Name:
- J/MNRAS/368/253
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep echelle spectrophotometry of the Galactic HII regions M16, M20 and NGC 3603. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10400{AA} range. We have detected more than 200 emission lines in each region. Physical conditions have been derived using different continuum and line intensity ratios. We have derived He^+^, C^++^ and O^++^ abundances from pure recombination lines as well as collisionally excited lines (CELs) for a large number of ions of different elements.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/L7
- Title:
- Faraday rotation of radio sources from THOR
- Short Name:
- J/ApJ/887/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present first results for Faraday rotation of compact polarized sources (1-2GHz continuum) in The HI/OH/Recombination line (THOR) survey of the inner Galaxy. In the Galactic longitude range 39{deg}<l<52{deg}, we find rotation measures (RMs) in the range -310rad/m^2^<=RM<=+4219rad/m^2^, with the highest values concentrated within a degree of l=48{deg} at the Sagittarius arm tangent. Most of the high RMs arise in diffuse plasma, along lines of sight that do not intersect HII regions. For l>49{deg}, RM drops off rapidly, while at l<47{deg}, the mean RM is higher with a larger standard deviation than at l>49{deg}. We attribute the RM structure to the compressed diffuse warm ionized medium in the spiral arm, upstream of the major star formation regions. The Sagittarius arm acts as a significant Faraday screen inside the Galaxy. This has implications for models of the Galactic magnetic field and the expected amount of Faraday rotation of fast radio bursts from their host galaxies. We emphasize the importance of sensitivity to high Faraday depth in future polarization surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A123
- Title:
- Far-IR study of G29.96-0.02
- Short Name:
- J/A+A/552/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- G29.96-0.02 is a high-mass star-forming cloud observed at 70, 160, 250, 350, and 500{mu}m as part of the Herschel survey of the Galactic plane (Hi-GAL) during the science demonstration phase. We wish to conduct a far-infrared study of the sources associated with this star-forming region by estimating their physical properties and evolutionary stage, and investigating the clump mass function, the star formation efficiency and rate in the cloud. We have identified the Hi-GAL sources associated with the cloud, searched for possible counterparts at centimeter and infrared wavelengths, fitted their spectral energy distribution and estimated their physical parameters.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A77
- Title:
- FEEDBACK from the NGC7538 HII region
- Short Name:
- J/A+A/659/A77
- Date:
- 14 Mar 2022 07:43:25
- Publisher:
- CDS
- Description:
- The interaction of expanding HII regions with their environmental cloud is one of the central questions driving the SOFIA legacy program FEEDBACK. We want to understand the interaction of the prototypical NGC7538 HII region with the neighboring molecular cloud hosting several active star-forming regions. Using the Stratospheric Observatory for Infrared Astronomy (SOFIA), we mapped an area of ~210'^2^ (~125pc^2^) around NGC7538 in the velocity-resolved ionized carbon fine-structure line [CII] at 1.9THz (158um). Complementary observed atomic carbon [CI] at 492GHz and high-J CO(8-7) data, as well as the archival near- and far-infrared, cm continuum, CO(3-2), and HI data are folded into the analysis. The ionized carbon [CII] data reveal rich morphological and kinematic structures. While the overall morphology follows the general ionized gas that is also visible in the radio continuum emission, the channel maps show multiple bubble-like structures with sizes on the order of ~80-100'' (~1.0-1.28pc). While at least one of them may be an individual feedback bubble driven by the main exciting sources of the NGC7538 HII region (the O3 and O9 stars IRS6 and IRS5), the other bubble-like morphologies may also be due to the intrinsically porous structure of the HII region. An analysis of the expansion velocities around 10km/s indicates that thermal expansion is not sufficient but that wind-driving from the central O-stars is required. The region exhibits a general velocity gradient across, but we also identify several individual velocity components. The most blue-shifted [CII] component has barely any molecular or atomic counterparts. At the interface to the molecular cloud, we find a typical photon-dominated region (PDR) with a bar-shape. Ionized C+, atomic C0 and molecular carbon CO show a layered structure in this PDR. The carbon in the PDR is dominated by its ionized C+ form with atomic C0 and molecular CO masses of ~0.45+/-0.1M_{sun}_ and ~1.2+/-0.1M_{sun}_, respectively, compared to the ionized carbon C+ in the range of 3.6-9.7M_{sun}_. This bar-shaped PDR exhibits a velocity-gradient across, indicating motions along the line of sight toward the observer. Even if it is shown to be dominated by two nearby exciting sources (IRS6 and IRS5), the NGC7538 HII region exhibits a diverse set of substructures that interact with each other as well as with the adjacent cloud. Compared to other recent [CII] observations of HII regions (e.g., Orion Veil, RCW120, RCW49), the bubble-shape morphologies revealed in [CII] emission that are indicative of expanding shells are recurring structures of PDRs.
